Construction of a mobile network requires a huge amount of funds, which brings heavy financial pressure to an operator. A network sharing technology can enable multiple operators to provide services for their respective subscribers by using a shared mobile network, significantly reducing costs for repeated construction of mobile networks. Currently, there are mainly four network sharing manners: (1) sharing a site; (2) sharing an access network; (3) sharing both an access network and a core network; (4) sharing a geographical area network.
A Long Term Evolution (Long Term Evolution, LTE for short) mobile communications system is used as an example. User equipment (User Equipment, UE for short) in an idle state initiates a service request procedure before sending uplink data. During an UE access process, the UE selects a previously registered mobility management entity (Mobility Management Entity, MME for short) as its serving MME. Therefore, an operator serving the UE does not change in a service access procedure. However, in a network sharing scenario, when moving from a network of operator A to a shared network on which both operator A and operator B can provide a service, a subscriber of operator B cannot select, in a timely manner, the home operator B of the subscriber as a serving operator of the subscriber.
In addition, in a network scenario in which an access network is shared, or in a network scenario in which both an access network and a core network are shared, an LTE mobile communications system is still used as an example. A base station (evolved NodeB, eNB for short) broadcasts, in a broadcast message, a list of operators supported by the evolved NodeB, that is, a public land mobile network (Public Land Mobile Network, PLMN for short) list. A UE reads the operator list (PLMN list) in the broadcast message, selects one PLMN from the operator list, and sends the selected PLMN to the eNB in a Radio Resource Control (Radio Resource Control, RRC for short) connection setup procedure, and the eNB selects a core network node of this operator for the UE according to the selected PLMN, to provide a service for the UE. However, when a core network node of an operator is overloaded, subsequent access of a subscriber of this operator cannot be controlled in the prior art. Moreover, in an enhanced network sharing scenario, when a quantity of access subscribers of an operator reaches an upper limit of a rented share, subsequent access of a subscriber of this operator cannot be controlled in the prior art. In addition, when a roaming subscriber accesses a shared network, load sharing cannot be performed among multiple operators. As a result, an operator ranking first in a broadcast list tends to be overloaded, or achieves an excessive income from roaming subscribers.